Ink jet printing is a non-impact method for producing images by the deposition of ink droplets on a substrate (paper, transparent film, fabric, etc.) in response to digital signals. Ink jet printers have found broad applications across markets ranging from industrial labeling to short run printing to desktop document and pictorial imaging. The inks used in ink jet printers are generally classified as either dye-based or pigment-based.
Pigment based inks have been gaining in popularity as a means of addressing these limitations. In pigment-based inks, the colorant exists as discrete particles. The problem is that these inks interact with specially coated image receiving substrates, such as transparent films used for overhead projection and the glossy papers and opaque white films used for high quality graphics, to produce cracked images.
U.S. Pat. No. 5,462,591, by Karandikar et al, discloses an aqueous phase change ink that contains dyes and block copolymers of polyethylene oxide and polypropylene oxides as thermogelling components that causes the ink to gel when its temperature is increased to its thermoinversion point. No pigments are included in these inks.